1. Field of the Invention
This invention relates generally to magnetic medical treatment aids and more particularly to flexible permanent magnetic sheets having an integrally formed pattern of magnetism for therapeutic use.
2. Description of the Prior Art
Various magnetically patterned sheet-type devices have been disclosed in the prior art as being useful for being applied over a part of a patient's body, the lumbar region for example, to stimulate blood flow and to reduce stiffness and pain. The present invention improves on the prior art in providing these benefits.
U.S. Pat. No. 3,921,620 to Nakayama and U.S. Pat. No. 4,480,596 to Shumiyashu disclose magnetic belts having a pattern of discrete permanent magnet discs received in circular holes arranged in a rectangular pattern in a substrate, such as a flexible magnetic material, for imparting a magnetic flux normal to the material in the lumbar region to reduce stiffness or pain.
U.S. Pat. No. 4,489,711 to Latzke discloses a magnetic plaster formed of an elastic magnetizable plastic sheet material, magnetized in a series of parallel stripes of alternating polarity, at a spacing of 4-10 mm. This arrangement is designed to enable positioning the sheet on the patient's skin with the stripes oriented transversely of the patients vasculature so that blood flow traverses the alternating poles.
U.S. Pat. No. 4,549,532 to Baermann discloses a magnetic sheet which strives to improve upon Latzke's design by arranging the magnetic poles in a pattern which is concentric, angular or radial about a common axis or center. This arrangement is intended to permit the patient to position the sheet in any orientation on the skin and still have the pattern traverse the underlying vasculature. Although an improvement over Latzke's arrangement in this regard, Baermann's approach has several limitations.
First, Baermann's patterns cannot be expanded indefinitely in size to cover large areas of a patient's body. As the pattern is scaled to larger sizes, the circumferential extent of each area of one polarity increases to the point where it is no longer effective to induce any changes in magnetic flux. For example, in the concentric case, each ring becomes very large at a distance spaced from the center, so large that an underlying blood vessel oriented tangentially of the pattern can travel a substantial distance without crossing a magnetic polarity boundary. The same thing can happen in the angular or radial pattern. Additionally, as the angular or radial pattern is enlarged, the lengths of segments increase so that a blood vessel, aligned lengthwise of the segment, does not necessarily cross areas of alternating polarity.
Second, the patterns of both Latzke and Baermann are integrally formed by magnetically imprinting them on the magnetic sheet, using a magnetizing fixture. In the case of Baermann's patterns, it is difficult to make an effective fixture to magnetically imprint these patterns, particularly those having sharp angular intersections between the areas of opposite polarity. It has also been proposed to use a checkerboard polarity pattern. This pattern would also be difficult to build and effective fixture for, because of the large number of right angles packed into a relatively small area. Besides the difficulties in making the fixture, the resulting magnetic fields formed in such small geometries will be blurred at the corners.
Accordingly, a need remains for a design for a therapeutic magnetic sheet having a pattern that will cross underlying vasculature with a high probability over a large area while being oriented freely on a patient's skin, and that is easy to imprint integrally into a flexible magnetic sheet.